TODAY | December 01, 2013
>>> let's begin with the power of the internet. a fifth grade teacher wants to teach her students about the dangers of posting photos. so she did a little experiment. and she tells us what happened next was a huge surprise even to her. here's janet shamlian .
>> reporter: when julie posted this photo on her facebook page, the tennessee teacher never dreamed some 5 million people would end up seeing it. or that her selfy would be altered in dozens of ways like this. and this. and with a tip of the hat to john madden like this.
>> i really wanted to have a way that i could show them how quickly things travel.
>> reporter: cope was lesson planning at indian lake elementary in hendersonville, tennessee. in the photo, she's holding a note that says, "i'm talking to my fifth grade students about internet safety and how quickly a photo can be seen by lots of people. if you are reading this, please click like. thanks!" within hours, thousands had liked and shared the photo on facebook . then it really took off. a worldwide audience in just a few days after it was reposted on various websites. views skyrocketed.
>> it was definitely a little overwhelming. i didn't expect that. that's kind of the lesson is to teach the kids that anyone can see it.
>> reporter: a lesson for julie as well. she changed her facebook privacy settings after discovering personal photos were publish viewable. and then there are the manipulations of julie 's original photo. the internet had a field day with it.
>> this teacher's experiment was fun. and it was relatively harmless. but it can have serious consequences from personal information to sense tiitive photography that you don't want people seeing, private details about your life.
>> reporter: even with the alterations, julie says she has no regrets.
>> i'm really pleased that it's been able to give other people something to talk about with their kids.
>> reporter: and how anyone can take liberties with an online photo. for "today," janet shamlian , nbc news.
>> i think lesson learned.
>> such a great lesson.
>> isn't it? she'll also find out that will live forever . another lesson of the internet.
>> for a long time.